1. Field of the Invention
The present invention relates to a method of preparing graphene and an anode mixture for a lithium secondary battery including graphene prepared thereby, and more particularly, to a method of preparing graphene by thermochemically reacting a crystalline carbide compound serving as a starting material with a halogen element-containing gas to give a porous carbide-derived carbon which is then oxidized and reduced, and to an anode mixture for a lithium secondary battery including graphene prepared thereby.
2. Description of the Related Art
Lithium ion secondary batteries for use in mobile phones, PDAs, digital cameras, camcorders, etc. are manufactured in such a manner that an oxide and a graphite, which are respectively utilized as a cathode material and an anode material for a chemical battery system, are mixed with an appropriate binder and conductor to give a slurry, followed by forming a cathode plate and an anode plate, which are then wound or stacked together with a separator to form a core cell, after which the core cell is encased, thus fabricating a lithium secondary battery having a cylindrical, prismatic and pouch shape.
Thorough research into performance improvements of lithium secondary batteries is ongoing, especially in the area of capacity and energy density. To this end, methods of enhancing performance of batteries through improvements of designs and development and improvement of materials are under study, but are dependent on development of electrode active materials, especially anode active materials.
Initially used as an anode active material for an anode of a lithium secondary battery is lithium metal. However, lithium has drawbacks of low reversibility and poor stability, and research into anode active materials for lithium secondary batteries is still ongoing.
Accordingly, a material for an electron emitting source may include a carbonaceous material, for example, carbon nanotubes having superior conductivity and field concentration and emission properties with low work function. However, carbon nanotubes are typically provided in the form of fibers having a high field enhancement factor, and materials having such a shape are problematic in terms of uniformity and lifetime. The fibers made of a paste, ink or slurry have inferior process problems compared to other materials in particle form, and furthermore, raw materials thereof are very expensive.
To solve the problems with carbon nanotubes, extensive and intensive research into use of graphene as an anode active material has been carried out. In particular, graphene is prepared using a Hummers method for oxidizing and reducing graphite. Graphite typically used in a Hummers method is highly crystalline non-porous carbon, and graphene prepared by highly crystalline non-porous carbon is composed mainly of macropores.
Recently, however, since electrode materials for secondary batteries, including electrodes for lithium secondary batteries, supercapacitors or flow capacitors, and movable electrodes, require graphene having micropores or mesopores, graphene having macropores prepared from highly crystalline non-porous carbon is difficult to use in electrodes for secondary batteries.